All Questions
16 questions
14
votes
4
answers
2k
views
Create a snail matrix
Statement:
Create a script that, given an integer \$n\$, create a square matrix of dimensions \$n \times n\$ with the numbers from \$1\$ to \$n^2\$, arranged in a snail pattern.
Example:
...
- 631
2
votes
3
answers
407
views
How can I optimize my Von Neumann neighborhood algorithm?
I am working on a small project that requires finding Von Neumann neighborhoods in a matrix. Basically, whenever there is a positive value in the array, I want to get the neighborhood for that value. ...
7
votes
1
answer
210
views
Computing sums of weird pattern in 2D array as efficiently as possible
This is a problem from Hackerrank (https://www.hackerrank.com/challenges/2d-array/problem). We're given a 6x6 (always) 2D array and asked to compute the sums of all the hourglass patterns in the array....
- 1,159
5
votes
1
answer
142
views
Naive Solver of Matrix with Periodic Boundary Conditions Feedback
I am creating an \$O(n)\$ solver for an \$Ax = b\$ system where \$A\$ has the form
\$
A = \begin{pmatrix}
a_1 & b_1 &&&d_{u}\\ c_1 & a_2 & b_2\\& \ddots & \ddots &...
- 201
7
votes
2
answers
3k
views
Magic Square (Python)
Problem
Write a method to return a boolean if an input grid is magic square.
A magic square is a \$NxN\$ square grid (where N is the number of cells on each side) filled with distinct positive ...
- 3,592
3
votes
1
answer
109
views
Decomposing a matrix as a sum of two bitstrings
I chanced upon this question and came up with the following algorithm, looking for criticisms and advice on how to improve my algorithm efficiency.
You are given 3 arguments:
A & B are ...
- 133
2
votes
1
answer
2k
views
Rotate matrix 90 degrees
I recently did problem 1.7 Rotate Matrix in Cracking the Coding Interview. I realized my code is very different than what is in the book and also from what I'm finding online (I'm having trouble ...
- 121
0
votes
1
answer
216
views
Greedy adaptive dictionary (GAD) for supervised machine learning [closed]
For my project in machine learning supervised, I have to simplify a training-data and I have to use this technique at page 5 of the document.
Pseudocode algorithm
My code (numbers are the steps):
<...
5
votes
1
answer
7k
views
Implementation of the Householder Transformation
I implemented the Householder transformation in Python, so that I can later use it in a QR decomposition. Unfortunately I haven't found a good concise source for reading up on the algorithm.
I am not ...
- 151
6
votes
1
answer
2k
views
Sparse matrix compressed sparse row (CSR) in Python 2.7
Brief introduction for CSR:
The compressed sparse row (CSR) or compressed row storage (CRS) format
represents a matrix M by three (one-dimensional) arrays, that
respectively contain nonzero ...
- 3,493
2
votes
1
answer
160
views
Internal method to calculate the distance between all nodes in Kruskal's Importance (Driver) Algorithm
I've been trying to reduce the indentation from a method in my code. The solution will probably be unrelated to the language, in this case python, although it may rely on some python specific ...
- 243
6
votes
4
answers
2k
views
Kadane's Algorithm for 2D array with known boundaries
I asked this question first on StackOverflow but I didn't get an answer and was advised to try here too. So here we go.
I have implemented Kadane's algorithm for a 2D array in Python 2 with known ...
- 163
11
votes
1
answer
5k
views
Matrix rotation algorithm
This is the Matrix Rotation problem from hackerrank.com.
You are given a 2D matrix, \$a\$, of dimension \$M×N\$ and a positive integer
\$R\$. You have to rotate the matrix R times and print the ...
- 305
4
votes
1
answer
1k
views
Point in a polygon algorithm
I am implementing a Point in polygon algorithm.
Inputs:
M, N: size of the matrix
poly: a ...
- 295
6
votes
1
answer
2k
views
Implementing the CutHill-McKee Algorithm
I am very much interested in the Reverse Cuthil McKee Algorithm. I have seen Fortran and C or C++ implementations of it, and I decided that it would be a nice exercise to implement it in Python.
I ...
- 497